MicroElectroMechanical (MEMS) microphones are known. Generally speaking, in these devices a MEMS device or die (including a diaphragm and back plate) is disposed on a substrate (e.g., a printed circuit board (PCB)). A lid (or other type of cover) is attached over the substrate to enclose the MEMS device and integrated circuit. A port is disposed either through the lid (to make a top port device) or through the substrate (to make a bottom port device). Sound enters the port, moves the diaphragm, electrical energy (representative of the sound energy) is created, and this energy can be further processed or used by other devices.
During the manufacturing process, gasses can build up within the assembly. Current bottom port microphones require a pierced diaphragm to relieve gases that build up within the interior of the microphone assembly. In pierced diaphragm approaches, a small opening is maintained in the diaphragm to release these built-up gasses. Without relieving these gases, the lid can bend or otherwise deform, internal components can become damaged, or both. Another problem that sometimes occurs because of the build-up of gasses within the assembly is that the acoustic seal that secures the lid to the substrate can become compromised. This creates leakage problems and adversely affects microphone performance.
While the previous pierced diaphragm approaches reduced damage to the assembly, acoustic noise was also introduced. The pierced diaphragm can also allow debris to enter the assembly and become trapped between the diaphragm and the back plate. These problems have created dissatisfaction with previous approaches.
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